The effect of magnetic stirring current on carbon segregation of 180 mm×180 mm cast billet of gear steel 20CrMnTiHl and the effect of change of residual B content in steel during refining and casting on hardenability of steel have been tested and analyzed. Results showed that as magnetic stiring current decreased from 200 A to 100 A
the carbon segregation index of cast billet decreased by 0.1;with controlling residual B in 20CrMnTiHl steel≤0.0002%
the hardenability band width of steel was ≤ 4 HRC.